UST912014I4

ABSTRACT

A PROCESS FOR APPLYING A PRECISELY UNIFORM SOLID COATING OF FLUID MATERIAL ONTO SOLID SUBSTRATE PARTICLES WHEREIN SAID PARTICLES ARE PREHEATED IN A ROTARY DRUM HAVING A RADIANT HEAT SOURCE SUCH THAT THE SURFACE IRREGULARITIES OF SAID PARTICLES ARE SMOOTHED OUT BY A COMBINATION OF SURFACE MELTING AND TUMBLING ACTION. THE PREHEAT PARTICLES ARE FED TO A SECOND ROTARY DRUM WHERE MULTIPLE, THIN, CONCENTRICALLY FORMED LAYERS OF THE COATING MATERIAL ARE APPLIED BY CASCADING THE SUBSTRATE PARTICLES BENEATH A PLURALITY OF SEQUENTIALLY APPLIED, CLOSELY CONTROLLED SPRAYS OF THE COATING MATERIAL. IN PARTICULAR, THE PROCESS ALLOWS THE COATING OF GRANULAR UREA WITH MOLTEN SULFUR APPLIED UNDER PRECISE SPRAYING TEMPERATURES AND CONDITIONS IN SUCH A MANNER THAT THE MOLTEN SULFUR EVENLY COATS THE PARTICLES AND SOLIDIFIERS WITH THE DESIRED PHYSICAL CHARACTERISTICS TO FORM A SLOW RELEASE NITROGEN FERTILIZER AT AN ECONOMICAL COST WITHOUT THE USE OF SUBCOATS, SEAL COATS, MICROBICIDES, PARTING AGENTS, OR PLASTICIZERS. FURTHER, IT IS SHOWN BY EXAMPLES THAT THE OPERATIONAL CONDITIONS AND TECHNIQUES PRESENTED HEREIN CONSTITUTE A SUBSTANTIAL IMPROVEMENT IN THE PROCESS FOR THE PRODUCTION OF SULFURCOATED UREA WHERE ADDITIONAL COATINGS CONSISTING OF MATERIALS OTHER THAN SULFUR ARE USED. A UNIQUE SPRAY HEADER FOR PNEUMATIC ATOMIZING SPRAY NOZZLES IS DESCRIBED WHICH INCLUDES THE INSTALLATION OF AN ORIFICE IMMEDIATELY EXTERNAL TO EACH NOZZLE. THE FLOW RATE OF LIQUID IS PROPORTIONAL TO EACH NOZZLE BASED ON THE AREA OF THE OPENING IN EACH ORIFICE. THE COATED PRODUCT IS RAPIDLY COOLED TO CONTROL CRYSTAL STRUCTURE OF THE APPLIED COATING MATERIAL.



